Battery Draining if Inverter Left On

[MTinOH]

For our off grid cabin, I installed 4 100W Renogy panels, a Renogy MPPT Charge Controller and connected it to a 100Ah Lithium battery. The battery then connects to a 2500W Pure Sine Wave Inverter and then into a breaker box.

The panels are not in an ideal location right now (lots of trees), and I hope to move them to an opening next year. If I leave the inverter off, the solar is enough to fully charge the battery during the days I'm gone (we are typically at our full time home on weekdays and at the cabin on the weekends). If I leave the inverter on, I come back the next weekend and the battery is almost dead. There is nothing that should be pulling power from the battery since we really just use it for lighting. Is an inverter really that big of an energy vampire or is there something else going on? Thanks for your thought!

 

[rmaddy]

Inverters do consume some power even at idle. Some use more than others. Some have settings that allow them to use a little less than normal.

Your battery is 12V 100Ah which is 1200Wh. 5 days x 24 hours/day is of course 120 hours. 1200Wh / 120 hours = 10W. So a 10W idle draw will completely drain the battery in 5 days if it's not being recharged at all. Your inverter might use 30W when idle. 1200Wh / 30W = 40 hours. So if your battery is not completely dead after 5 days then it must be getting some solar charging in during the week. But either way it's not surprising that your battery is low by the next weekend if the inverter is left on. Check your inverter manual or data sheet for something like a "zero load power" or "idle load power" value in watts.

Also note that a 2500W inverter on a 12V 100Ah battery only gives you less than 30 minutes of usage if you are using the full wattage and you drain the battery a full 100%. Most likely you are not using that much power but 100Ah of battery is really small for such a large inverter. And the larger an inverter the more they tend to drain at idle.

 

[John Frum]

For our off grid cabin, I installed 4 100W Renogy panels, a Renogy MPPT Charge Controller and connected it to a 100Ah Lithium battery. The battery then connects to a 2500W Pure Sine Wave Inverter and then into a breaker box.

The panels are not in an ideal location right now (lots of trees), and I hope to move them to an opening next year. If I leave the inverter off, the solar is enough to fully charge the battery during the days I'm gone (we are typically at our full time home on weekdays and at the cabin on the weekends). If I leave the inverter on, I come back the next weekend and the battery is almost dead. There is nothing that should be pulling power from the battery since we really just use it for lighting. Is an inverter really that big of an energy vampire or is there something else going on? Thanks for your thought!

I suggest you get a shunt based battery monitor.
Knowledge is power.

 

[wkyongae]

According to the specifications of the inverter it draws 2amps so if you multiply 2amps times 12vdc you get 24watts. Thats the power draw of the inverter. Now multiply 12vdc times 100ah battery you get 1200watt hours. 1200watt hour divided by 24watts is 50 hours. Now considering you don't get all of that and depending on how your inverter is setup could be far less hours as voltage drops. Short answer yes the inverter is a power hog. I didn't add in the charge controller as they typically don't draw much. If I'm wrong someone will correct me.

 

[Wellbuilt]

This inverter is high Quality and has a very low power draw and it can stay in stand buy using less power .

 

[rmaddy]

This inverter is high Quality and has a very low power draw and it can stay in stand buy using less power .

That's only a 300W inverter. The OP has a 2500W inverter. The idle power tends to get higher with bigger inverters.

 

[RV10flyer]

My shop’s 12V 2500W Zantrex (1997) and 3500W EDECOA (2021) HF inverters draw 0.8 and 0.9 A at idle. I turn them off at night, even with 571 aH of LFE capacity. Yes, you have a power hog at 2.0 A

My Daly BMS’s draw 0.015 A.

Also, your LFE loses a very small amount per day, even more with grade B cells.

 

[Wellbuilt]

That's only a 300W inverter. The OP has a 2500W inverter. The idle power tends to get higher with bigger inverters.

Yes I under stand that but , he states he uses it for led lites ?
This inverter has stand buy mode and burns very little power when on .
400 watts of solar and 100ah battery is just to small for 2500 watt inverter

 

[RV10flyer]

Yes I under stand that but , he states he uses it for led lites ?
This inverter has stand buy mode and burns very little power when on .
400 watts of solar and 100ah battery is just to small for 2500 watt inverter

He said he has it wired into his electrical panel.

 

[RV10flyer]

For our off grid cabin, I installed 4 100W Renogy panels, a Renogy MPPT Charge Controller and connected it to a 100Ah Lithium battery. The battery then connects to a 2500W Pure Sine Wave Inverter and then into a breaker box.

The panels are not in an ideal location right now (lots of trees), and I hope to move them to an opening next year. If I leave the inverter off, the solar is enough to fully charge the battery during the days I'm gone (we are typically at our full time home on weekdays and at the cabin on the weekends). If I leave the inverter on, I come back the next weekend and the battery is almost dead. There is nothing that should be pulling power from the battery since we really just use it for lighting. Is an inverter really that big of an energy vampire or is there something else going on? Thanks for your thought!

I would cut a few trees vs moving pv panels too far from house on a 12V system. Also, you’ll need to keep LFE batteries above 32F if you want to charge them. You could always take battery home with you and bring it back charged on the weekend.

 

[Wellbuilt]

He said he has it wired into his electrical panel.

? I have mine wired to my panel , it works good .
The unit is hard wire only , mine ran my 2800 sf cabin lites tv radio cell booster .
I ran small hand tools and charged Makita battery’s .
With 400 watts of solar and 100ah battery he can’t use a 2500 watt inverter .
I think the 300 watt inverter manual wants a 200ah battery

 

[sunshine]

The panels are not in an ideal location right now (lots of trees),

...and will get worse as the northern winter sets in.

Start with your first, and obvious, reason before going onto the next-
Even a 20w idle draw over 24hrs is probably more than the average daily output of your 400w panels at this time of year.

 

[12VoltInstalls]

What is the issue with turning off the inverter when not present?

(Just curious: that 300W hardwired inverter… does it automatically reset if it trips on overload? Or does it just go to sleep?)

 

[RV10flyer]

? I have mine wired to my panel , it works good .
The unit is hard wire only , mine ran my 2800 sf cabin lites tv radio cell booster .
I ran small hand tools and charged Makita battery’s .
With 400 watts of solar and 100ah battery he can’t use a 2500 watt inverter .
I think the 300 watt inverter manual wants a 200ah battery

I didn’t see where he said he was using it for just LED lights.

 

[12VoltInstalls]

didn’t see where he said he was using it for just LED lights.

There is nothing that should be pulling power from the battery since we really just use it for lighting

I think there’s an assumption of LEDs

 

[circus]

After some thought my idea was bad so I deleted it.

 

[MTinOH]

Thanks to everyone who responded, this forum is such an a wealth of knowledge with so many kind, helpful people.

For clarity, yes it is primarily just LED lighting and sometimes a fan that we are using in the cabin. I got a larger inverter "just in case" we needed it for things like plugging in a vacuum or running power tools, but at the time wasn't thinking about the energy usage consequences. I have been taking the battery home and charging it as needed when needed, but hoping I can get the panels to do the work for me (other than on the coldest weeks when I might need to take it home).

I'm seeing a theme of a few different solutions in the suggestions:

1) Keep Everything the Same but Make Sure to Shutoff the Inverter - This is likely going to be my short term solution but it is a bit frustrating to know that my battery is going to slowly run down from the inverter even when I'm using it.

2) Smaller Inverter - I happen to also own a 2000W Krieger Inverter that only consumes 0.5A at idle. Only part that is a little tricky for me is that it only a standard plug to connect to it instead of terminals for hardwiring. I hear I can rig an extension cord to wire it to the breaker box though.

3) Upsize - I assume if I added a few more panels and another battery, it would start to outpace the power used by the inverter. It will sure help when I can get out of the deep forest and get the panels better exposure.

Let me know your thoughts on the best of the options above and thanks again.

 

[Wellbuilt]

What is the issue with turning off the inverter when not present?

(Just curious: that 300W hardwired inverter… does it automatically reset if it trips on overload? Or does it just go to sleep?)

I have never faulted the unit ?
It would allmost start my frig but I turned it off when it did not work .
If the battery voltage gets low it starts freaking out flashing yellow light and beeping but still never turned off .
I’ve run a 15amp Makita saws all but it runs at half speed .
Drills run good .
My place uses 2/300 watts max even with the frig on but the little inverter won’t start it
The thing seams bullet proof .

 

[Wellbuilt]

I think there’s an assumption of LEDs

It would be crazy to use any thing but led lites off grid .
Here is my place At dark
I had some chicken in my ceramic egg .?
the place is using less then 200 watts now and shoots up to 300 if the frig kicks on .
I have 19+ led lites on plus radio I don’t really have to keep tract of it , I just use as much power as I want .
If I run the micro wave in the morning before sun up and the frig kicks on I’ve had the inverter fault but the girls where cooking some thing for 20 mins

 

[rmaddy]

yes it is primarily just LED lighting and sometimes a fan that we are using in the cabin.

Use simple 12VDC LEDs - no inverter required. Use a 12VDC fan - no inverter required.

Assuming you currently use LED lights that require 110VAC and a regular 110VAC fan then it would be a lot cheaper to buy 12VDC versions of those two than it would be to buy another battery or more solar panels. Save the inverter for the rare times, while on site, you need to plug in something that really needs 110VAC.

Keep in mind that even a 0.5A idle power draw is 6W. That will still use 60% (720Wh) of your battery in 5 days.